Hi, I am having a somewhat similar problem with my Gateway laptop, using my rather inferior troubleshooting skills I have not reached any conclusions.
It is a 400 series laptop, and It won´t turn on at all, with the battery in or out, plugged in or unplugged. Power is getting to the laptop because the green icon for the battery in front of the computer lights up, but not the icon for the AC power.
I havent been able to figure out if the Gateway 400 series is capable of running on AC power with the battery removed. If it is I guess that means I have a more serious problem than a dead battery, even though that kind of sucks too, if I have to get a new one just to run it off of AC power.
One thing, the computer, or battery, ¨died¨when I was running it on
the battery and then plugged in the AC adaptor. After that it froze up and then the screen went black, not to turn on again.

Any theories? Any help will be greatly appreciated, Thanks, -Daniel